Location: GREAT PLAINS AGROCLIMATE AND NATURAL RESOURCES RESEARCH
2021 Annual Report
Objectives
Objective 1: Develop new and enhance existing model components and methodologies to better estimate long term trends, variations, and uncertainty in future water availability due to climate change.
Objective 2: Determine the impacts of future variation or change in water availability on soil erosion, crop productivity, and resilience and sustainability of managed agricultural lands.
Objective 3: Develop long-range planning information for policy makers, environmental organizations, and conservation planners on potential future water availability, cropland productivity, and water and soil conservation options that would maintain or increase the resilience and sustainability of agricultural lands.
Objective 4: Develop science-based, region-specific information and technologies for agricultural and natural resource managers that enable climate-smart decision-making and transfer the information and technologies to users.
Approach
The Earth’s climate is warming and will likely continue to warm for the rest of this century. In the Southern Great Plains of the U.S., droughts are expected to increase in frequency, duration, and severity, and storm events to become more intense. Climate change poses a new set of challenges affecting future water availability, agricultural soil resources, and long term sustainability of rainfed crop production systems in the Southern Great Plains. The extent of climate change impacts on agriculture at the end of the century is unclear, and information on management strategies and conservation options to effectively adapt to and mitigate the detrimental effects of climate change is limited. This applied, goal-driven investigation uses available projections of precipitation, air temperature, and carbon dioxide levels through year 2100, and relies on agricultural system models to simulate impacts of climate change scenarios on rainfall-runoff, soil erosion, and sustainability of crop production systems. Long term land management strategies, agronomic options, and conservation measures that enhance future water availability, reduce soil erosion, and improve the sustainability of cropping systems are explored, and uncertainties in projected impacts are estimated. Effectiveness and risk of various strategies and options to reduce or offset climate change impacts are determined by evaluation of probability distributions of climate change impacts. Findings are expected to support national and regional strategic planning of alternative long term adaptive conservation measures that maintain effective, competitive, sustainable, and environmentally responsible agricultural cropping systems under changing and uncertain future climatic conditions.
Progress Report
Sub-objective 2A: Research continued on calibrating and evaluating the Water Erosion Prediction Project (WEPP) model for simulating spatial distribution of soil erosion in small watersheds. Five input files including weather, soil, topography, watershed configuration and structure, and crop management including tillage operations were compiled for three small watersheds in Coshoction, Ohio for the period of 1950 to 2015 (65 years total). Runoff volumes and sediment yields from each rainfall event during 1950-2015 were also collected and compiled for each watershed. Spatial erosion distribution at a 10-m grid during 1950-2015 was estimated using measured activity (similar to elemental concentration) of the radionuclide cesium 137 (Cs-137), and the proportional sediment contributions between overland erosion and ephemeral gully erosion were also estimated with Cs-137 for each watershed. The WEPP model was calibrated sequentially as follows. First, a key soil water conductivity parameter was varied or calibrated to match WEPP-simulated runoff volumes with the measured volumes. Second, soil erodibility parameters (reflecting soil’s susceptibility to erosion) were calibrated to match WEPP-simulated sediment yields with the measured yields. Third, soil erodibility for ephemeral gully erosion was checked and calibrated if needed to make sure the proportional sediment contribution from the gully was similar to the proportion estimated using Cs-137 for each watershed. The second and third steps were repeated as needed. The calibrated WEPP model were used to simulate the spatial distribution of soil erosion. The WEPP-simulated spatial erosion patterns are being compared with those estimated by Cs-137 for each watershed to assess the WEPP model’s ability to simulate spatial variation of soil erosion along hillslopes and ephemeral gully in each watershed. The results should be useful for improving the physically based WEPP model in simulating spatial variation of soil erosion. (Objective 2, sub-objective 2A)
Accomplishments
1. Simulated effects of climate change and crop management systems on soil erosion. Increased climate variability and extremity under climate change will have adverse impacts on agricultural production and environmental protection. Proper simulation of such impacts is imperative for policy makers and producers to develop strategic plans for soil and water conservation and for mitigation of the adverse impacts of climate changes. ARS scientists in El Reno, Oklahoma downscaled 100 climate scenarios, projected by 25 Global Climate Models (GCM) under two greenhouse gas emission levels, to the Weatherford station in Oklahoma using two statistically downscaling tools that specifically consider the frequency and magnitude of extreme precipitation events. Both tools were parameterized for the present climate, and then modified according to the GCM-projected climate change signals for generating future climate. Four common tillage systems and 11 cropping systems were simulated for crop management. Tillage systems included conventional till, conservation till, no-till, and delayed till. Crops included winter wheat, soybean, sorghum, canola, and cotton, which were planted in continuous monoculture or in rotation with alfalfa. Compared with the present climate, future precipitation at the station would decrease by about 5%, and crop yields decline by 10 to 20% except cotton due to decreased precipitation and rising temperature. Despite a decrease in precipitation, surface runoff and soil loss would increase slightly by <7% and <30%, respectively, due to increased occurrence of extreme rainfall events. Results showed that no-till systems are most effective in reducing soil erosion, followed by crop rotations with alfalfa. These results would be useful to policy makers, soil and water conservationists, and producers regarding how to adapt to climate change by adjusting cropping and tillage systems in central Oklahoma to keep soil loss below the tolerable levels.
Review Publications
Chen, J., Zhang, X.J. 2021. Challenges and potential solutions in statistical downscaling of precipitation. Climatic Change. 165(63):1-19. https://doi.org/10.1007/s10584-021-03083-3.
Chen, J., Brissette, F.P., Martel, J., Zhang, X.J., Frei, A. 2021. Relative importance of internal climate variability versus anthropogenic climate change in global climate change. Journal of Climate. 34(2):465-478. https://doi.org/10.1175/JCLI-D-20-0424.1.
Li, A., Zhang, X.J., Liu, B. 2021. Effects of DEM resolutions on soil erosion prediction using Chinese soil loss equation. Geomorphology. 384:107706. https://doi.org/10.1016/j.geomorph.2021.107706.
Wang, L., Zheng, F., Liu, G., Zhang, X.J., Wilson, G.V., Shi, H., Liu, X. 2021. Seasonal changes of soil erosion and its spatial distribution on a long gentle hillslope in the Chinese Mollisol region. International Soil and Water Conservation Research. https://doi.org/10.1016/j.iswcr.2021.02.001.
Zhang, X.J., Shen, M., Chen, J., Homan, J.W., Busteed, P.R. 2021. Evaluation of statistical downscaling methods for simulating daily precipitation distribution, frequency, and temporal sequence. Transactions of the ASABE. 64(3). https://doi.org/10.13031/trans.14097.
Chen, H., Liu, G., Zhang, X.J., Shi, H. 2021. Quantifying sediment source contributions in an agricultural catchment with ephemeral and classic gullies using 137Cs technique. Geoderma. 398:115112. https://doi.org/10.1016/j.geoderma.2021.115112.
